1. Field of the Invention
The present invention relates to a ceramic color composition and a method for producing a glass sheet.
2. Discussion of Background
Heretofore, a glass sheet provided with a ceramic color layer for an automobile has been widely used, which has been prepared by screen printing a ceramic color composition in a paste form along the periphery of a window glass of an automobile, followed by drying and baking in a step of heating the glass sheet for bending.
Such a ceramic color paste forms a colored opaque layer when baked along the peripheral portion of a glass sheet. This is employed for the purpose of preventing deterioration of a urethane sealant due to ultraviolet rays, or preventing electric heating wire terminals from being seen through from the exterior of the car, by the opaque layer.
As a composition for such a purpose, it is known to mix various heat resistant color pigments to a base material of low-melting point non-crystal line glass or crystallized type glass which usually contains lead as the main component. However, with respect to the material containing lead, which used to be mainly employed, it is desired to develop a substitute containing no lead from the viewpoint of e.g. recycling.
The present inventors have previously proposed a bismuth type material as a ceramic color composition which contains no lead and which is excellent in a release property (Japanese Unexamined patent publication No. 234547/1994 and U.S. patent application Ser. No. 08/314,290). U.S. patent application Ser. No. 08/314,290 proposes also a ceramic color composition having metallic Si powder added to a Bi type glass powder. However, such a composition tends to be slightly yellowish by the addition of the metallic Si powder.
The previously proposed material is basically excellent. However, it has been apparent by now that as compared with the conventional lead type material, it has a problem that the strength of the glass sheet having the ceramic color paste baked thereto, is slightly low.